Multiple choice

A 225 m long train is running at a speed of 30 km/hr. How much time does it take to cross a man running at 3 km/hr in the same direction?

  1. 40 seconds

  2. 30 seconds

  3. 25 seconds

  4. 15 seconds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Relative speed = 30 - 3 = 27 km/hr = 27 * (5/18) = 7.5 m/s. Time = Distance / Speed = 225 / 7.5 = 30 seconds.

AI explanation

Since the man is running in the same direction as the train, their relative speed is calculated by subtracting the man's speed from the train's speed, yielding 30 km/hr minus 3 km/hr, equaling 27 km/hr. Converting this relative speed to metres per second gives 27 multiplied by 5 over 18, which simplifies to 7.5 metres per second. The time taken to cross the man is the train's length divided by the relative speed, resulting in 225 divided by 7.5, which equals 30 seconds.

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